Text Output Tab

Short Circuit Reports

Five different text reports are available during short circuit analysis: Momentary, Interrupting, 30 cycle, Equipment Duty, and Voltage Sensitivity. You can view the results onscreen or print them. EasyPower can display multiple result windows at one time and you can study them using the Window > Tile features.

Note: The ability to automatically check equipment duties during analysis is only available if you have purchased the SmartDuty™ option to EasyPower.

Text output to the result windows are independent of one-line output.

For example, you might want to study detailed text results of momentary and 30 cycle currents while displaying equipment duty results on the one-line. To do this, select the Momentary and 30 cycle check boxes in the Text Output tab of the Short Circuit Options dialog box. Click Equipment Duty. When a fault operation is done, EasyPower automatically applies the necessary faults for duty analysis and displays the results on the one-line. In addition, the momentary and 30 cycle faults are performed and displayed in the text result windows.

Note: The voltage sensitivity operation only tabulates momentary text results, regardless of what you might have chosen for the one-line's voltage sensitivity display.

The fuse interrupting currents are displayed in the High and Low Voltage Momentary result window since fuses open under momentary currents.

Fuse multiplying factors are based on the fault point X/R ratio and the fuse test X/R ratio. The interrupting currents are calculated by adjusting the symmetrical current if the equipment test X/R is less than the fault point X/R ratio. The following equation is used to determine the currents:

^Iadjsym ^=Isym [1 + 2e^{{-4πÁsys /(X/Rsys)}}]^1/2 / [1 + 2e^{{-4πÁsys /(X/RTest)}}]^1/2

Á= 0.49 - 0.1 e^-(X/R)/3}

Standard test X/R ratios are 5, 8, 12, and 15 for distribution and power fuses1IEEE Standard Design Tests for High Voltage Fuses, Distribution Enclosed Single Pole Air Switches, Fuse Disconnecting Switches, and Accessories, C37.41-1988..

This option lets you display ANSI standard interrupting duty currents for high voltage breakers. The breaker interrupting results are displayed in the High Voltage Interrupting result window according to the interrupting time chosen under the Cycles option (3, 5, & 8 cycles).

The interrupting currents are calculated by adjusting the symmetrical current by a multiplying factor. For breakers, the multiplying factor is based on the fault point X/R ratio, the No AC Decay (NACD) ratio, the contact parting time of the breaker, and whether the breaker is rated on a Total or Symmetrical basis. The NACD ratio consists of two factors dependent upon whether generation is Local or Remote. The equations and calculation procedures are too detailed for this discussion. If additional information is required refer to Reference2Sample System for Three Phase Short Circuit Calculations, Conrad St Pierre, IEEE/IAS Mar/Apr 1990.,3Interpretation of New American National Standards For Power Circuit Breaker Applications, Walter C. Huening Jr., IEEE/IAS Sept/Oct 1969.,4AC High Voltage Circuit Breakers Rated on a Symmetrical Current Basis, ANSI/IEEE Std. C37.010-1979..

This option displays low voltage power circuit breaker (LVPCB) and molded case circuit breaker (MCCB) interrupting currents for low voltage momentary faults. The results are displayed in the Low Voltage Momentary result window. Notice that under ANSI terminology, when the term interrupting is used for low voltage equipment, it applies to momentary or 1/2 cycle faults. This is because low voltage equipment typically interrupts within 1/2 cycle of fault inception.

The interrupting currents are calculated by adjusting the symmetrical current if the equipment test X/R is less than the fault point X/R ratio5Low Voltage Power Circuit Breakers Used in Enclosures, ANSI/IEEE Std. C37.13-1981.,6Low Voltage Power Circuit Breakers, NEMA Publications BU-195x, and BU1-1972.. The following equation is used to determine the currents:

^Iadjsym ^{= I}sym [1 + e{-^{2πÁ/(X/Rsys)}} ] / [1 + e^{{-2πÁ/(X/RTest)}} ]

Á= 0.49 - 0.1 e^{-(X/R)/3}

X/Rtest = TAN[ARCCOS(Tested PF)]

Three types of text output styles are available, ANSI, Symmetrical Components, and GE. The ANSI style is designed for reporting all the significant ANSI Standard breaker comparison multipliers and results for standard protective relaying requirements. If you select the ANSI output style, three different output formats are available. Levels 1-3 provide the standard format designed for equipment duty comparison and relaying currents. Level 3 contains the most detailed information.

The symmetrical component style is designed specifically for specialized relaying purposes that require a component output for both voltages and current. You are encouraged to try different options and levels of details for your particular study requirements.

The other option is GE, which is the popular General Electric short circuit format.

Displays generator and utility voltages and currents for each fault.